The present invention relates to the delivery of electrical energy to bodily tissues for therapeutic purposes, and more specifically to devices and methods for treating various disorders resulting from nerve transmissions in the brain.
The use of electrical stimulation for treatment of medical conditions has been well known in the art for nearly two thousand years. Electrical stimulation of the brain and the peripheral nervous system and/or direct stimulation of malfunctioning tissue is generally a completely reversible and non-destructive treatment and holds significant promise for the treatment of many ailments.
Deep brain stimulation (DBS) is a surgical treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain. DBS in select brain regions, such as the frontal cortex, has provided remarkable therapeutic benefits for otherwise treatment-resistant movement and affective disorders, such as chronic pain, Parkinson's disease, obsessive-compulsive disorder, major depression, essential tremor and dystonia. Although the exact principles and mechanisms of DBS are still not clear, DBS apparently changes brain activity directly in a controlled manner.
In addition to currently recognized neural circuits associated with behavioral disorders, there is an increasing awareness that abnormal neural activity in the brain may be associated with a variety of deleterious behavior patterns. For example, while obesity is not uniformly recognized as a class of psychiatric behavioral disorder, there is recent clinical evidence demonstrating that hyperphagia (excessive appetite and consumption of food) can be associated with excessive activity in certain neural circuits.
Deep brain stimulation systems typically consist of three components, the implanted pulse generator (IPG), the lead and the extension. The IPG is a battery-powered neurostimulator encased in a titanium housing, which sends electrical pulses to the brain to interfere with neural activity at the target site. The lead is a coiled wire insulated in polyurethane with four platinum iridium electrodes connected to the IPG by the extension, an insulated wire that runs from the head, down the side of the neck and behind the ear to the IPG. The IPG is typically placed subcutaneously below the clavicle, or in some cases, the abdomen.
DBS leads are placed in the brain according to the type of symptoms to be addressed. For non-Parkinsonian essential tremor, the lead is typically placed in the ventrointermedial nucleus (VIM) of the thalamus. For dystonia and symptoms associated with Parkinson's disease (rigidity, bradykinesia/akinesia and tremor), the lead is typically placed in either the globus pallidus or subthalamic nucleus.
Unfortunately, deep brain stimulation generally involves the invasive placement of electrodes into deep brain structures, along with the subcutaneous implantation of the electrical generator with batteries. Such approaches are expensive and generally accompanied by risks associated with surgery. In particular, implantation of the electrodes have risks associated with surgically accessing tissues of the brain, such as bleeding and infection. In addition, these approaches suffer from device-related risks, including device failure, battery-life limits and the like
Deeper areas of the brain are difficult to reach with current DBS techniques without damaging otherwise healthy areas of the brain. A recent improvement over DBS is to stimulate the brain noninvasively. Newer techniques like transcranial magnetic stimulation have attempted to accomplish this and have shown efficacy in treating depression. However, they have not been able to target small regions of the brain and require large, expensive devices to deliver currents sufficient to induce electric fields in the brain capable of depolarizing nerve membranes.
In light of the above, improved systems, devices and methods for the treatment of disorders associated with nerve transmissions in the brain are desired. In particular, it would be desirable if these systems and methods could help mitigate the debilitating effects of behavioral and other disorders without imposing excessive surgical trauma on the patient, and without having to damage or kill healthy neural tissues.